This invention relates to reciprocating type operating heads that travel automatically through successive variable-speed, variable-function operating cycles that include linear extension and retraction to and from a space within which predetermined operations are to be sequentially performed. More particularly, the invention relates to an apparatus for moving the operating head automatically through the desired cycle and especially where the head travels past working surfaces, such as dies for forming metals, between operating cycles of the dies, such as in die-casting, and performs certain functions, such as, but not limited to, spraying a lubricant on the surfaces and at other times emitting an air blast to remove flash, and the like, formed at parting lines, and to cool the working parts.
In many industrial forming processes, such as the molding, die-casting, drawing and forging of metals and other materials, it is common practice to apply a lubricant to the working surfaces between each forming cycle. At the same time, while the mold or die sections are separated, other operations are often performed, such as blowing air against the forming surfaces to remove any residual flash that many remain around the die cavities, and also blowing air or spraying air and water to cool surfaces which are difficult to cool with the integral circulating cooling system normally provided. The lubricant, which is generally in liquid or powdered form, improves the flow of the metal or other material being formed, reduces wear of the working parts, and facilitates removal of the newly-formed product from the mold or die. Often two different types of liquid are to be sprayed during an operating cycle.
To apply the lubricant automatically and thus avoid the necessity of having a worker move between the opposed platens of an open die or mold between cycles, mechanical reciprocating devices are commonly used. These devices move a spray head past the surfaces of the mold or die to be lubricated while the platens are separated, and spray intermittently so as to apply the lubricant to the desired surfaces. Such devices commonly have air blast nozzles as well to help cool various working parts and also to remove flash.
When the forming cycles are repeated quite rapidly, it is necessary to move the spray head and associated equipment at high speed between the open die sections, since the dwell time during which the mold or die platens remain open after removal of the newly-formed part is relatively short. Since it is normally difficult to speed up the actual spraying time and still achieve effective lubrication, it is most important that the time intervals during which the equipment is not spraying be kept as short as possible. Accordingly, a relatively fast speed of travel is used during nonspraying movement and a somewhat slower speed, or complete stop, is used when lubricating material is being sprayed.
The state of the art in this field is shown by the following patents and other publication:
______________________________________ U.S. Pat. No. To Issued ______________________________________ 3,482,652 Stone III Dec. 9, 1969 2,929,564 Stone III March 22, 1960 2,344,905 Short March 21, 1944 3,525,382 Devol Aug. 25, 1970 3,522,838 Ott Aug. 4, 1970 2,695,592 Szczepanski Nov. 30, 1954 3,393,658 Ott July 23, 1968 3,544,355 Ott Dec. 1, 1970 954,241 Affelder and Gorton April 5, 1910 3,870,164 Haase March 11, 1975 3,699,592 Miller June 13, 1972 3,998,388 Alagna Dec. 21, 1976 3,463,399 Ott Aug. 26, 1967 4,041,899 Wolfe and Heath Aug. 16, 1977 German Patent Specification No. Issued 1,296,743 Jan. 22, 1970 and the following publications: Acheson Technical Brochure, entitled "Dag Swing Arm Reciprocator for automatic spraying of pressure die casting dies" Rimrock Corp. technical data sheet for Reciprocator Model 001, Model 002, Manifold and Nozzle Assemblies Model 104 Rimrock Corp. technical report No. 3 entitled "How problem tooling runs more profitably at Kolsters Tool and Die" G-W Plastics Engineers, Inc., technical bulletin 300R ______________________________________
Most of the prior art devices in the references listed above utilized fluid-drive means, such as hydraulic or pneumatic cylinder-and-piston assemblies. The fluid cylinders require high pressure seals in order to prevent fluid leakage and these seals are subjected to continual wear, as well as high temperatures, due to close proximity to the dies or molds, thus requiring periodic replacement in order to prevent a malfunction of the device.
A few devices utilize purely mechanical drive means, such as screw-and-ball-nut-type drive, as shown in U.S. Pat. No. 4,041,899, however, in each case the device, in order to provide the necessary length of travel of the operating head, is exceptionally long and since most are mounted over the machine or molding apparatus to be serviced, considerable overhead height is required, at least a height equal to the length of the reciprocating path of travel of the operating head. Many installations, however, do not have sufficient height overhead and thus are severely limited as to utilization of the particular space.
Another problem that has been encountered with prior art apparatus resides in the necessity to use flexible hoses, or other flexible conduits, to connect between the fixed parts of the device, a manifold, for example, to the reciprocating fluid emission head. Due to the repeated reciprocating movement, the hose is continually flexing and is subject to considerable wear leading to leakage and failure. While one device (U.S. Pat. No. 3,998,388) utilizes telescoping tubes to convey fluid from a fixed manifold to the moving fluid emission head, the device encounters the problem of accommodating the volume of fluid that is displaced when the head is retracted and the telescoping tube assembly is collapsed. The resulting need to force the fluid into an accumulator imposed undesirable stresses on the pumping system and conduits and renders the device impractical.
Another disadvantage of prior art devices is the limitations as to motion and spray functions that can be achieved during a particular cycle. Prior art devices often use timers to control the operating cycles and while these are satisfactory, they often require continuous readjustments due to changes in speed, for example, that occur due to temperature changes in the equipment and particularly in the fluid used to drive the operating head.
The device of the present invention, however, reduces the difficulties indicated above and affords other features and advantages heretofore not obtainable.